“Mehran, age 6, first arrived at her kindergarten in Kabul as Mahnoush, in pigtails and a pistachio dress. When school shut down for a break, Mahnoush left and never returned. Instead a short-haired, tie-wearing child with the more masculine-sounding name of Mehran began first grade with the other children.

Nothing else changed much. Some teachers were surprised but did not comment except to one another. When the male Koran teacher demanded Mehran cover her head in his class, a baseball cap solved the problem. Miss Momand, a teacher who started her job after Mehran’s change, remembers being startled when a boy was brought into the girls’ room for afternoon nap time but realizing, as she helped Mehran undress, that she was a girl. Mehran’s mother Azita later explained to Miss Momand that she had only daughters, and that Mehran went as the family’s son. Miss Momand understood perfectly. She herself used to have a friend at school who was a family’s only child and had assumed the role of a son.

Officially, girls like Mehran do not exist in Afghanistan, where the system of gender segregation is among the strictest in the world. But many other Afghans, too, can recall a former neighbor, a relative, a colleague, or someone in their extended family raising a daughter as a son. These children even have their own colloquialism, bacha posh, which literally translates from Dari to “dressed like a boy.” Midwives, doctors, and nurses I’ve met from all over the provinces are more familiar with the practice than most; they have all known bacha posh to appear at clinics, escorting a mother or a sister, or as a patient who has proven to be of another birth sex than first presumed.

The health workers say that families who disguise their daughters in this way can be rich, poor, educated, or uneducated, or belong to any of Afghanistan’s many ethnic groups. The only thing that binds the bacha posh girls together is their families’ need for a son in a society that undervalues daughters and demands sons at almost any cost. They disguised their girls as boys because the family needed another income through a child who worked and girls aren’t allowed to, because the road to school was dangerous and a boy’s disguise provided some safety, or because the family lacked sons and needed to present as a complete family to the village. Often, as in Kabul, it is a combination of factors. A poor family may need a son for different reasons than a rich family, but no ethnic or geographical reasons set them apart.

And to most of them, the health workers told me, having a bacha posh in the family is an accepted and uncontroversial practice, provided the girl is turned back to a woman before she enters puberty, when she must marry and have children of her own. Waiting too long to turn someone back could have consequences for a girl’s reputation. A teenage girl should not be anywhere near teenage boys, even in disguise. She could mistakenly touch them or be touched by them, and be seen as a loose and impure girl by those who know her secret. It could ruin her chances of getting married, and she would be seen as a tarnished offering. The entire family’s reputation could be sullied. For that reason, and because the bacha posh I spoke to were minors, some names and details have been changed in the story that follows.”